Sounding Board

Thu, 2010-04-08 12:21

Regarding declining public "belief" in global warming ("A Cooling Trend in Global Warming," From the Editor, November 2009): As engineers, our code of ethics requires that we hold paramount the safety, health, and welfare of the public. We, therefore, have an obligation to familiarize ourselves with the science of global warming. Anyone who can make sense out of a psychrometric chart should have no problem understanding what is happening, what is causing it, and what the implications for life on our planet are. An hour or two reviewing Intergovernmental Panel on Climate Change (IPCC) materials should cover the fundamentals. The IPCC's Fourth Assessment Report even contains a chapter specific to residential and commercial buildings.

Most of us are familiar with what research shows regarding building energy use. Buildings are responsible for one-third of global energy-related carbon-dioxide emissions. The buildings sector offers the largest low-cost potential for reduction of greenhouse-gas emissions, and co-benefits of these reductions—lower utility bills, increased real-estate value, better thermal comfort, greater productivity, and improved indoor- and outdoor-air quality—already are selling points we use as HVAC engineers.

Sadly, the impacts of climate change are becoming increasingly visible and harder to deny. With a clear atmospheric warming trend; accelerated melting of ice sheets, glaciers, and ice caps; and record ocean temperatures, we have every reason to participate vigorously in the green-building process. By helping to achieve a low-carbon future, we provide valuable benefits to our clients while keeping the welfare of the global public in mind.William Bishop, EIT, LEED APPathfinder Engineers & Architects LLPRochester, N.Y.

HPAC Engineering needs to remain factual. Most engineers have little tolerance for continual references to "global warming," whether the writer means well or not. It is perfectly acceptable to focus on real, measurable benefits of reduced toxins, energy efficiency, actual fuel savings, and so forth without deflating the credibility of other claims by even mentioning global warming in the same sentence.

There are many examples of this, and it appears the authors do not realize the effect on an intelligent audience.

Because we know the latest warming cycle ended during the last decade, it is not unreasonable to expect that even the uneducated masses inevitably will lash back at such fraudulent justifications for investment, let alone government subsidies, programs, and new so-called "carbon taxes."

As professionals, our focus must be on factual information and bottom-line benefits to our clients, which are measured not by invented claims of "carbon saved" or "global warming avoided," but in real terms of toxins (e.g., nitrogen oxide, metals) reduced and cubic feet of gas, kilowatt-hours, and dollars saved.Name withheld, LEED APMarion, Ill.

David Sellers' perversion of the concept of pollution ("Greenhouse-Gas Impacts," Sounding Board, March 2010, http://bit.ly/aWG15B) is typical of the extremes to which enviro-activists can go.

The thing that is polluting has to be a harmful substance foreign to what it is being added to. Adding sugar to a bowl of sugar will not pollute the sugar; adding, say, salt will.

Carbon dioxide (CO2) is not a harmful substance. It is added to soft drinks to make them "fizz." It is the fizz in beers and ales. Adding CO2 to air does not in any sense pollute the air. CO2 already is in the air.

The amount of CO2 in the air generally is reported to be about 0.035 percent. The effect CO2 has on global warming at that concentration is for all practical purposes negligible. The major component providing the greenhouse effect is, by far, water vapor. Without some amount of greenhouse effect, the planet will freeze, and we all will die.

What would happen if we doubled or tripled the CO2 concentration? The effect still would be negligible. One possibility is greater plant growth and food production for increasing populations.John HampeDedham, Mass.

Chilled Beams As I was reading the article "Chilled Beams" by Peter Rumsey, PE, CEM, FASHRAE, FRMI, in the January 2010 issue of HPAC Engineering, a question came to mind: Whether you are using active or passive chilled beams, how will the testing-and-balancing firm balance the system? Are there any balancing dampers on the air nozzles (for the active type) or balancing valves on the beams?Mohamed M. ElsayedBurns & McDonnellKansas City, Mo.

Author's response: Active chilled beams are supplied with both air and water. On the air side, we typically put a manual balance damper on each chilled beam in the same way you would a standard air diffuser. The water can be balanced manually with a manual balance valve or automatically with a pressure-independent balance valve. We normally have one control valve per zone or group of chilled beams. On some projects, we have skipped all balance valves and relied on the two-way valve to be self-balancing. More people are choosing to omit automatic balancing valves in favor of the self-balancing action of two-way valves. On the water side, passive chilled beams can be treated the same as active chilled beams.Peter Rumsey, PE, CEM, FASHRAE, FRMIRumsey Engineers/Integral GroupOakland, Calif.

Non-chemical Treatment The December 2009 article "Greening Your Cooling Tower" was pretty good, but I think it missed two very important points in its discussion of non-chemical water treatment.

The first is that non-chemical treatment methods do not work with all water chemistries. Careful analysis of system makeup water as part of the application process is a very important component of a successful installation. The second is that non-chemical systems require the same level of monitoring, maintenance, and care as any chemical program.

The problems with non-chemical systems we hear about usually stem from a system being installed where it should not have been and/or being hung on the wall and walked away from. They are not "plug-and-play" devices.

Finally, any discussion of "greening" cooling towers needs to address the issues faced by owners of new galvanized towers. Depending on makeup chemistry, proper passivation, which is essential to the life of galvanized cooling towers, may need to involve chemicals.Brad BolinoJohn J. Kirlin LLCRockville, Md.

'The Case for Increased Ventilation' The following comments, concerning the March 2010 article "The Case for Increased Ventilation" by David Harlos, ScD, and Michael West, PhD, PE, were posted on HPAC.com via the Disqus comment system.

"Carl Luther" wrote: "Companies are under ... various pressures, just as employees are. The current 'green' movement discourages increased ventilation—indeed, LEED (Leadership in Energy and Environmental Design) standards encourage ventilation based on the percentage of CO2 (carbon dioxide) in return-air streams. With corporations setting goals driving ever-greater efficiency and ... energy-consumption/greenhouse-gas reductions, this becomes a good practice that likely never will see implementation (because of) opposing goals. Sick workers simply need to stay home, and people at work need to utilize good hygiene practices to limit increased contamination of the workforce."

In response, author Harlos wrote: "Energy-crisis conservation requirements drove down ventilation rates during the 1970s. That, combined with the rising tide of chemical use inside buildings, initiated the 'indoor-air-quality' field. Current demands for energy efficiency and conservation and more refined methods of regulating indoor air lie behind further restriction of outside air. It is our contention that we once again are paying significant unrecognized costs by not looking at all of the benefits of greater ventilation. The greatest challenge is reducing carbon footprints at the same time. We have good tools to meet that challenge through clever engineering practice, but as you point out, there are non-engineering tools (in this case, human resources [HR]) that can be combined with engineering to maximize health impacts. Unfortunately, coordinating these multidisciplinary approaches is difficult. For example, how many HR managers do you suppose read this article?"

"peter dinkledorf" wrote: "The author(s) assume that there are other individuals at the sick employee's place of employment (who) are able to do the work and that there is time in the project schedule to allow the sick employee to be absent.

"I, unfortunately, appear to have neither. I am not an egotist when I say that if I don't do it, it won’t get done.

"Employers today do not have extra staff available to reassign, nor do they seem to care if the ventilation system is working properly. Some Scrooge-like business owners would just as soon do without paying for employee 'benefits' of any kind.

"So, dream on, Mr. Author. Dream on."

In response, author Harlos wrote: "We do dream, as you can see from our article. Sick leave is supposed to be built into any business schedule, and when it is not or when it effectively is discouraged, as you suggest, there are great costs to the individual employee and to the business itself. This is a false economy for such a business. Because the costs are not tracked does not mean they are not incurred. Likewise, such policies are recognized by employees and no doubt take a further toll through low morale and its many outcomes. We can't address these issues with ventilation, but we can point out to savvy owners that they have unrecognized and largely unexploited resources at their disposal to partially control health-care costs and improve other outcomes at the same time. It is following that positive path that we dream about."

Pressurization ControlThank you for publishing the very useful article on building pressurization control by Dave Moser, PE ("Pressurization Control in Large Commercial Buildings," February 2010). What I liked: It's well-written, it discusses a common issue in today's buildings, it concisely describes the problem and possible sources, it has good diagrams, it provides multiple solutions, it references useful articles for further reading, and it provides useful clues for discovering the problem.Donald C. Schock, PECJL EngineeringMoon Township, Pa.

"charlesbeach" wrote: "Your views on correct synchronization of SA (supply-air) and RA (return-air) fans are right on the mark universally.

"In actual practice, pressure sensing OA (outside air) to inside is not technically demonstrable as yet and may not be feasible, given the effects of wind.

"Closed-loop volumetric synchronization with altitude offsets for changing elevation using a traceable reference has worked previously on buildings such as the Sears Tower and the Hancock building(s), if stack effect is of concern."

To which the author replied: "Good point about stack effect. The article does not specifically address stack effect as it relates to building pressurization. The strategy you suggested—volumetric synchronization—is another method of pressurization control and was mentioned in the article. This could be the best strategy for tall buildings. However, depending on the situation, it could be difficult to retrofit into an existing system because of the space requirements of the airflow-measuring stations."

"robertstan" wrote: "In commissioning, if you take manual control of return-fan speed and run from stopped to 100 percent, you would be unlikely to see a change in building pressurization, especially vs. a wind or in a high-rise.

"In 'large' buildings with multiple air-handling units, just the inaccuracy of static-pressure sensors and control-loop tuning prevents this from working.

"Sounds good on paper, but doesn’t work!"

To which the author replied: "It's true wind can have a great effect on building pressure and that high-rise buildings have additional challenges related to building pressurization that must be addressed. I'd be hesitant to write off building-pressurization systems because of these challenges, though. Adequate shielding from wind effects (as best as possible at least), calibration of static-pressure sensors, and proper tuning of control loops are necessary for an active building-pressurization-control strategy to work properly.

"Regarding return fans, research and case studies have shown that return-fan operation does have an effect on building pressurization."

Rooftop-Unit Selection The following comments, concerning the February 2010 article "Simplifying the Selection of Rooftop Units" by Kenneth M. Elovitz, PE, Esq., were posted on HPAC.com via the Disqus comment system.

"leonardlotz" wrote: "Every calculation system seems to have a built-in safety factor so that no one undersizes the total capacity of the unit. This leads to oversizing, with poor performance results. In my location, the standard design temperature for commercial HVAC is 75 degrees at 95 degrees OAT (outside-air temperature). Last year, we had about 16 hr of that condition all year long. That means (for) the balance of the year, all the systems were oversize(d) and inefficiently operating. You will notice in most commercial HVAC units, the manufacturer is going to multistage cooling equipment to correct that condition (3- to 25-ton compressors in place of one 75-ton unit). More economical designs use multiple single-stage units that cover zones of similar loads. Engineers seem to be afraid of designing systems to meet the load of (a) building and feel that if 50 tons is good, 75 to 100 tons would be better."

"Awesome Engineer" wrote: "There are many factors that affect the sizing of air-conditioning equipment, and installation is one of them. Sometimes, a correctly sized unit may not deliver the specified amount of air (because of) poor installation, which includes not only improperly sealing the ductwork, but ... contractors choos(ing) not to follow carefully laid-out plans for ductwork. Often, they will use cheaper field-fabricated tees and elbows, rather than the radius type that engineers show on the plans. To account for this, sometimes engineers must 'oversize' the equipment because they have little control over how the contractors ultimately install the ductwork. Unfortunately, when the system doesn’t cool properly, the engineer will be spending his non-compensated time trying to troubleshoot and explain why. If contractors would follow the plans, rather than doing it the cheap way or how they 'always have done it,' they might be surprised to find out how well these systems can work."

In reply to "Awesome Engineer," "guest" wrote: "So, you are compensating for the shoddy installation/work that you think the contractor likely will perform and then on your non-compensated time you are troubleshooting their performance. Perhaps you should enhance and make more clear your drawing notes and specs and clean up your 'cell library' every once in a while.